This invention relates to an air conditioning system using an air cycle.
A conventional refrigerator operating through an air cycle is disclosed, for example, in xe2x80x9cShin-ban Reito-Kucho-Binran Dai-4-han Kiso-henxe2x80x9d pp.45-48, published by Japan Society of Refrigerating and Air Conditioning Engineers. Alternatively, a heating system in which an air cycle is used to form a heat pump is disclosed in xe2x80x9cAIRAH JOURNALxe2x80x9d June 1997 pp.16-21, published by The Australian Institute of Refrigeration Air Conditioning and Heating. Hereinafter, this heating system will be described.
As shown in FIG. 9, the above heating system comprises a heat source side channel (a) and a heat application side channel (f). The heat source side channel (a) is formed by connecting a compressor (b), a first heat exchanger (c), a second heat exchanger (d) and an expander (e) in this order and arranged to operate through an air refrigeration cycle. On the other hand, the heat application side channel (f) is formed by connecting the second heat exchanger (d), a humidifier (g) and the first heat exchanger (c) in this order.
Further, in the heat source side channel (a), when the compressor (b) is driven, a room air being discharged for ventilation is taken in the compressor (b) and compressed therein. The compressed air sequentially flows through the first heat exchanger (c) and the second heat exchanger (d), is expanded in the expander (e) and is then discharged to outdoors. On the other hand, in the heat application side channel (f), an outside air being supplied to the room for ventilation is taken in and sequentially flows through the second heat exchanger (d), the humidifier (g) and the first heat exchanger (c). During this flow, the outside air is heated through heat exchange with the air of the heat source side channel (a) in both the heat exchangers (d, c) and humidified in the humidifier (g). The system provides heating for the room by heating and humidifying the outside air taken in the heat application side channel (f) and then supplying it to the room.
As described above, in the conventional heating system, the room air taken in the heat source side channel (a) does nothing but to sequentially flow through the compressor (b), both the heat exchangers (c, d) and the expander (e). Therefore, the following problems arise.
The actual air contains a certain amount of moisture. The air reaches a low temperature through expansion in the expander. Therefore, moisture in the air is condensed so that water droplets will be ejected together with the air from the expander. Further, when the heating system is operated as a heat pump, the temperature of the air undergoing expansion often drops to sub-zero Celsius temperatures. In this case, moisture in the air may be frozen into ice and ejected as snow combined with the air.
This problem is highlighted particularly in such a structure that supplies a room air to the compressor as in the above-described heating system. Specifically, during heating, the absolute humidity of a room air is generally higher than that of an outside air. Therefore, the air higher in absolute humidity than the outside air will be discharged from the compressor. As a result, not only moisture in the air may be condensed at the expansion, but also moisture in the air discharged from the expander may be condensed and blown out as mist.
Accordingly, the conventional heating system requires a structure for disposing of water droplets and ice discharged together with the air from the expander. Particularly, when the system has caused freezing, the processes of defrosting ice and then draining off defrosted water are needed. This creates the need for components for such processes and therefore induces the problem that the system construction is complicated.
On the contrary, if the air temperature at the inlet of the expander is elevated and the air temperature at the outlet of the expander is thereby increased, it can be prevented that moisture in the air discharged from the expander is condensed. Therefore, the above problem can be avoided. In this case, however, it is necessary to increase the input to the compressor in order to ensure a required heating capacity. This induces the problem of decreasing the COP (coefficient of performance).
If a structure is adopted which supplies an outside air to the heat exchanger in order to cool the compressed air as for example in the above-described heating system, the air temperature at the inlet of the expander may be reduced to provide improved COP because during heating the outside air is generally at a relatively low temperature. In this case, however, the air temperature at the outlet of the condenser cannot be reduced enough to avoid the above-described problem resulting from moisture condensation. Therefore, it is impossible to reduce the air temperature at the inlet of the expander to provide improved COP.
The present invention has been made in view of the foregoing points and therefore has its object of maintaining a high COP and concurrently providing a simplified construction of the system by eliminating the need for drainage and snow removal processes.
The present invention provides for dehumidifying an air, which works in an air cycle, in a portion of the cycle upstream of an expander (22) until the air reaches the absolute humidity of an outside air or below.
More specifically, a first solution taken in the present invention is directed to an air conditioning system that is formed with an air cycle circuit (20) including a compressor (21), a heat exchanger (30) and an expander (22) and configured to provide heating for a room by heating a secondary air through heat exchange with a primary air of the air cycle circuit (20) in the heat exchanger (30) and then supplying the heated secondary air to the room. Further, the system is provided with dehumidifying means (55, 60) for dehumidifying the primary air so that the absolute humidity of the primary air is equal to or below the absolute humidity of an outside air, the dehumidifying means (55, 60) being disposed in a portion of the air cycle circuit (20) upstream of the expander (22).
In a second solution taken in the present invention, based on the first solution, the primary air is an exhaust air being discharged from the room to outdoors or a mixed air of the exhaust air and an outside air and is discharged to outdoors through the expander (22), while the secondary air is an inlet air being supplied from outdoors to the room or a mixed air of the inlet air and a room air and is supplied to the room through the dehumidifying means (55, 60).
In a third solution taken in the present invention, based on the second solution, the dehumidifying means (55, 60) is arranged to supply to the secondary air moisture having been removed from the primary air.
In a fourth solution taken in the present invention, based on any one of the first to third solutions, the dehumidifying means (55) is disposed in a portion of the air cycle circuit (20) located between the compressor (21) and the expander (22) and arranged to dehumidify the primary air compressed by the compressor (21).
In a fifth solution taken in the present invention, based on the fourth solution, the dehumidifying means (55) includes a separation membrane configured so that vapor in the air is permeable from higher side to lower side in vapor partial pressure of the separation membrane, and is arranged to separate vapor from the primary air without condensation.
In a sixth solution taken in the present invention, based on the fifth solution, the separation membrane is formed of a polymer film and configured so that vapor permeates therethrough by diffusion of water molecules into the membrane.
In a seventh solution taken in the present invention, based on the fifth solution, the separation membrane has a large number of pores of substantially the same size as a free path of molecules and configured so that vapor permeates therethrough by capillary condensation and diffusion of water molecules.
In an eighth solution taken in the present invention, based on the fifth solution, the dehumidifying means (55) is arranged to contact one surface of the separation membrane with the compressed primary air and contact the other surface thereof with the secondary air to transfer vapor in the primary air to the secondary air.
In a ninth solution taken in the present invention, based on the fifth solution, pressure reducing means (36) is provided for reducing the pressure of one side of the separation membrane of the dehumidifying means (55) to ensure a difference in vapor partial pressure between both sides of the separation membrane.
In a tenth solution taken in the present invention, based on any one of the first to third solutions, the dehumidifying means (55) is disposed in a portion of the air cycle circuit (20) upstream of the compressor (21) and arranged to dehumidify the primary air to be supplied to the compressor (21).
In an eleventh solution taken in the present invention, based on the tenth solution, the dehumidifying means (60) includes a humidity medium for absorbing and releasing moisture through contact with an air and arranged to allow the humidity medium to absorb moisture in the primary air to be supplied to the compressor (21) while releasing the moisture therein to the secondary air thereby continuously dehumidifying the primary air.
In a twelfth solution taken in the present invention, based on the eleventh solution, the humidity medium of the dehumidifying means (60) is provided with a solid adsorbent for adsorbing moisture.
In a thirteenth solution taken in the present invention, based on the twelfth solution, the humidity medium of the dehumidifying means (60) is formed of a rotor member (61) that is formed in the shape of a disc to allow air passage in a direction of its thickness and provides contact of the passing air with the solid adsorbent, and the dehumidifying means (60) is provided with a moisture absorbing section (62) where the rotor member (61) absorbs moisture in the primary air through contact with the primary air, a moisture releasing section (63) where the rotor member (61) releases moisture therein to the secondary air through contact with the secondary air, and a drive mechanism for rotatively driving the rotor member (61) to allow the rotor member (61) to move between the moisture absorbing section (62) and the moisture releasing section (63).
In a fourteenth solution taken in the present invention, based on the twelfth solution, the solid adsorbent is made of porous inorganic oxide.
In a fifteenth solution taken in the present invention, based on the eleventh solution, the humidity medium of the dehumidifying means (60) comprises a liquid absorbent for absorbing moisture.
In a sixteenth solution taken in the present invention, based on the eleventh solution, the humidity medium of the dehumidifying means (60) comprises a liquid absorbent for absorbing moisture, and the dehumidifying means (60) is arranged so that the liquid absorbent is heated by the primary air coming from the compressor (21) to release moisture having absorbed from the primary air to the secondary air.
In a seventeenth solution taken in the present invention, based on the fifteenth or sixteenth solution, the dehumidifying means (60) includes a moisture-permeable, hydrophobic porous membrane and is arranged to contact the liquid absorbent with the primary air through the hydrophobic porous membrane.
In an eighteenth solution taken in the present invention, based on the fifteenth or sixteenth solution, the liquid absorbent is made of a water solution of hydrophilic organic compound.
In a nineteenth solution taken in the present invention, based on the fifteenth or sixteenth solution, the liquid absorbent is made of a water solution of metallic halide.
In a twentieth solution taken in the present invention, based on the fifteenth or sixteenth solution, the dehumidifying means (60) comprises a circulation circuit (64) that includes a moisture absorbing section (65) for contacting the liquid absorbent with the primary air and a moisture releasing section (66) for contacting the liquid absorbent with the secondary air and circulates the liquid absorbent between the moisture absorbing section (65) and the moisture releasing section (66).
A twenty-first solution taken in the present invention is, based on any one of the eleventh to twentieth solutions, provided with humidity adjusting means (90) for adding part of moisture being released from the humidity medium to part of the secondary air supplied to the dehumidifying means (60) and then supplying the part of the secondary air to the room, while adding the remaining part of moisture being released from the humidity medium to the remaining part of the secondary air, cooling and dehumidifying the remaining part of the secondary air through heat exchange with the secondary air not yet supplied to the heat exchanger (30) and then supplying the remaining part of the secondary air to the room.
In the first solution, the air cycle circuit (20) operates through an air cycle in a manner that the primary air flows through the compressor (21), the heat exchanger (30) and the expander (22) in this order. In the heat exchanger (30), the secondary air undergoes heat exchange with the compressed primary air so that it is heated. Then, the heated secondary air is supplied to the room thereby providing heating for the room. On the other hand, the primary air is dehumidified by the dehumidifying means (55, 60) so as to reach the absolute humidity of the outside air or below before it arrives at the expander (22). Therefore, even if the temperature of the primary air at the outlet of the expander (22) is set lower than the outside air temperature, it can be prevented that water droplets or ices are produced in the primary air at the outlet of the expander (22).
In the second solution, an air containing at least an exhaust air from the room is taken in as a primary air, flows through the compressor (21), the heat exchanger (30) and the expander (22) in this order, and is then discharged to outdoors. This air is dehumidified by the dehumidifying means (55, 60) before it arrives at the expander (22). Further, an air containing at least an inlet air from outdoors is taken in as a secondary air, is heated through heat exchange with the primary air in the heat exchanger (30), and is then supplied to the room.
In the third solution, the dehumidifying means (55, 60) effects removal of moisture from the primary air and supply of the moisture to the secondary air. In other words, in the dehumidifying means (55, 60), the moisture removed from the primary air is used to humidify the secondary air.
In the fourth solution, moisture is removed from the primary air, which has been compressed by the compressor (21), by the dehumidifying means (55).
In the fifth solution, since the dehumidifying means (55) includes the given separation membrane, moisture in the compressed primary air is separated from the primary air while maintaining its vapor state.
In the sixth or seventh solution, the separation membrane is configured to allow vapor to permeate therethrough in the given course.
In the eighth solution, the compressed air contacts one surface of the separation membrane, while the secondary air contacts the other surface thereof. Accordingly, in operating conditions where the vapor partial pressure of the secondary air is lower than that of the primary air, moisture in the primary air is transferred to the secondary air without any external action being placed thereon.
In the ninth solution, a difference in vapor partial pressure between both sides of the separation membrane can be ensured by the pressure reducing means (36). In other words, the separation membrane is contacted on one surface thereof by the compressed primary air and reduced in pressure on the other surface side thereof by the pressure reducing means (36). Accordingly, the vapor partial pressure on the other surface side of the separation membrane can be maintained lower than the primary air.
In the tenth solution, the primary air dehumidified by the dehumidifying means (55) is supplied to the compressor (21).
In the eleventh solution, the humidity medium of the dehumidifying means absorbs moisture in the primary air and releases the absorbed moisture to the secondary air. In other words, the moisture in the primary air is continuously transferred to the secondary air through the humidity medium. This provides continuous dehumidification of the primary air and continuous humidification of the secondary air.
In the twelfth solution, the humidity medium absorbs moisture in such a manner that the moisture is adsorbed on the solid adsorbent. Further, the humidity medium releases moisture in such a manner that the moisture is desorbed from the solid adsorbent.
In the thirteenth solution, the humidity medium is formed of a disc-shaped rotor member (61). A portion of the rotor member (61) absorbs moisture through contact with the primary air in the moisture absorbing section (62). The rotor member (61) is rotatively driven by the drive mechanism so that the portion of the rotor member (61) which has absorbed moisture moves to the moisture releasing section (63). In the moisture releasing section (63), the rotor member (61) releases the moisture through contact with the secondary air. The rotor member (61) as the humidity medium is thereby regenerated. Thereafter, the portion of the rotor member (61) which has been regenerated moves to the moisture absorbing section (62) again and repeats these actions.
In the fourteenth solution, the solid adsorbent is made of porous inorganic oxide. It is to be noted that the solid adsorbent may be made of particular inorganic oxide alone or may include the inorganic oxide as a main ingredient.
In the fifteenth solution, the humidity medium absorbs moisture in such a manner that the moisture is absorbed in the liquid absorbent. Further, the humidity medium releases moisture in such a manner that the moisture is desorbed from the liquid absorbent.
In the sixteenth solution, the liquid absorbent absorbs moisture from the primary air not yet supplied to the compressor (21). This liquid absorbent is heated up into an easy-to-release condition by the high-temperature primary air compressed by the compressor (21), and then released to the secondary air. This moisture release regenerates the liquid absorbent.
In the seventeenth solution, the primary air and the liquid absorbent come into indirect contact with each other through the hydrophobic porous membrane interposed therebetween. The moisture in the primary air permeates the hydrophobic porous membrane and is then absorbed in the liquid absorbent, whereby the primary air is dehumidified.
In the eighteenth solution, the liquid absorbent is made of a water solution of hydrophilic organic compound. Examples of organic compound of this kind include ethylene glycol, glycerin and hydrophilic resin.
In the nineteenth solution, the liquid absorbent is made of a water solution of metallic halide. Examples of metallic halide of this kind include LiCl, LiBr and CaCl2.
In the twentieth solution, the liquid absorbent absorbs moisture of the primary air in the moisture absorbing section (65), whereby the primary air is dehumidified. This liquid absorbent flows through the circulation circuit (64) to reach the moisture releasing section (66). In the moisture releasing section (66), the liquid absorbent releases moisture to the secondary air, so that it is regenerated and the secondary air is humidified. The regenerated liquid absorbent flows through the circulation circuit (64) to reach the moisture absorbing section (65) again, and repeats this circulation.
In the twenty-first solution, the humidity medium in the dehumidifying means releases moisture to the secondary air, so that it is regenerated and the secondary air is humidified. The humidified secondary air is then supplied to the room through the humidity adjusting means (90). During the time, part of the secondary air takes part of moisture being released by the humidity medium and is then supplied to the room as it is. On the other hand, the remaining part of the secondary air takes the remaining part of moisture being released by the humidity medium, is cooled through heat exchange with the secondary air yet to be supplied to the heat exchanger (30) so that moisture in the secondary air is removed by condensation, and is then supplied to the room. In short, only part of moisture released from the humidity medium is supplied to the room together with the secondary air.
Thus, according to the present invention, since the primary air dehumidified to or below the absolute humidity of the outside air by the dehumidifying means (55, 60) expands in the expander (22), this prevents production of water droplets or ice in the primary air at the outlet of the expander (22) and also condensation of moisture in the primary air having been blown out of the expander (22) and concurrently enables the temperature of the primary air at the outlet of the expander (22) to be set lower than the outside air temperature. Therefore, the temperature of the primary air at the inlet of the expander (22) can be set still lower. Accordingly, while the quantity of heat given to the secondary air in the heat exchanger (30) is maintained, the input to the compressor (21) can be reduced. As a result, the COP can be enhanced. And concurrently water droplets or the like can be prevented from being produced in the primary air exiting from the expander (22) thereby eliminating the need for drainage and snow removal processes. Thus, the construction of the system can be simplified.
Particularly in the second solution, an air containing an inlet air from outdoors is used as the secondary air. Since the outside air temperature during heating is generally relatively low, such a low-temperature air containing an inlet air from outdoors is supplied as the secondary air to the heat exchanger (30). Therefore, the primary air can be cooled to a low temperature in the heat exchanger (30) so that the temperature of the primary air at the inlet of the expander (22) can be set at a low temperature. As a result, while the quantity of heat given to the secondary air in the heat exchanger (30) is maintained, the input to the compressor (21) can be reduced. This further ensures enhancement in the COP. Also in this case, the primary air is dehumidified to or below the absolute humidity of the outside air by the dehumidifying means (55, 60). Therefore, a drainage process and a snow removal process can be omitted thereby simplifying the construction of the system.
Further, in the second solution, an air containing an exhaust air coming from the room is used as the primary air, while an air containing an inlet air coming from outdoors is used as the secondary air. Therefore, the room can be ventilated while air conditioned. Furthermore, since the primary air containing the exhaust air is compressed by the compressor (21) and the compressed primary air is then heat exchanged with the secondary air containing the inlet air in the heat exchanger (30), hot heat can be recovered which is contained in the exhaust air being discharged to outdoors for ventilation. As a result, energy loss involved in ventilation can be reduced.
Still further, according to the third solution, moisture removed from the primary air can be used to humidify the secondary air. This eliminates the need for supplying additional moisture for humidification of the secondary air, which provides simplified construction. In addition, when all of the moisture removed from the primary air is supplied to the secondary air, there will be no need to dispose of the moisture as a drain. This also provides simplified construction.
Still further, according to the fifth to ninth solutions, moisture in the primary air can be separated from the primary air without being condensed. Therefore, energy taken by dehumidification of the primary air can be reduced to a larger extent as compared with the case of removing moisture by condensing it. This provides enhanced energy efficiency.
Particularly according to the eighth solution, moisture in the compressed primary air can be supplied to the secondary air as it is held in a vapor state. Thus, moisture will not evaporate in the secondary air in humidifying the secondary air. Accordingly, the heating capacity can be improved by recovering energy of vapor in the primary air to the secondary air, which provides enhanced energy efficiency.
Still further, according to the ninth solution, the difference in vapor partial pressure between both sides of the separation membrane can be ensured by the pressure reducing means (60), regardless of the operating conditions. Accordingly, means for removing moisture can always separate vapor from the compressed primary air for dehumidification of the primary air.
Still further, according to the eleventh to twentieth solutions, moisture in the primary air can be continuously transferred to the secondary air by the humidity medium of the dehumidifying means (60), which enables continuous dehumidification of the primary air and continuous humidification of the secondary air. Particularly according to the twelfth to twentieth solutions, the humidity medium of the dehumidifying means (60) can be formed using the solid adsorbent or the liquid absorbent. Further, according to the thirteenth and twentieth solutions, the dehumidifying means (60) can be formed properly for each particular humidity medium.
Still further, according to the twenty-first solution, the humidity medium of the dehumidifying means (60) can supply to the room only part of moisture being released to the secondary air. The secondary air having taken the moisture from the humidity medium may have an absolute humidity higher than that of the room air. In such a case, if the secondary air is supplied to the room as it is, the room humidity may have so risen as to give an uncomfortable feeling to a person present in the room. In contrast, according to this solution, it is possible to supply to the room so much only of moisture being released by the humidity medium as is necessary to maintain the room humidity, which makes it possible to maintain the room comfortably.